IMPAIRED ANTIBODY-RESPONSES TO PNEUMOCOCCAL POLYSACCHARIDE IN ELDERLYPATIENTS WITH LOW SERUM VITAMIN-B-12 LEVELS

Objective: To determine whether immunocompetent elderly patients with low serum vitamin B-12 levels have impaired serum antibody responses t o the 23-polyvalent pneumococcal polysaccharide vaccine. Design: Contr olled, prospective cohort study. Measurements: 15 patients with low se rum vitamin B-12 levels and 15 age- and diagnosis-matched patients wit h normal levels were vaccinated. Serum antibody titers to 12 pneumococ cal serotypes were measured by radioimmunoassay before and 4 weeks aft er vaccination. Results: The difference between the geometric mean of the vaccine anti body titers before a nd after vaccination for all 12 serotypes was lower (P = 0.005) in the patients with low vitamin B-12 levels than in the patients with normal levels. When mean corpuscular volume and age were controlled for, vitamin B-12 remained an independe nt predictor of antibody response (P = 0.005). Erythrocyte mean corpus cular volume was also an independent predictor of the increase in tite r (P = 0.03). Conclusions: Patients with low vitamin B-12 levels had i mpaired antibody responses to pneumococcal vaccine. Further study is n ecessary to determine whether treatment with vitamin B-12 can enhance specific immunoglobulin synthesis and improve the clinical efficacy of the pneumococcal vaccine in patients with low vitamin B-12 levels.